Woman injured while walking behind frozen US waterfall

Part of a frozen waterfall has come crashing down on a woman’s head after she trespassed behind it.

A video uploaded to Facebook by witness Judy Babcock shows the moment the wall of ice came crashing down at Minnehaha Falls in Minneapolis on Saturday afternoon.

The 20-year-old woman was taken to hospital with injuries to her wrist and arm, according to Minneapolis Park Board spokesperson Robin Smothers.

Ms Smothers said the park board did all they could to warn thrill-seekers against jumping barricades and wandering behind the frozen waterfall.

"Every year we tell people to be safe and view them from the pavilion or on the foot bridge," she told the Star Tribune.

"We just ask that people who want to see this beautiful frozen falls view it from the two safe and legal areas, either the footbridge directly above the falls or the pavilion area," she was quoted by MPR News as saying.

This is the first injury reported this year, but there were two last year.